Aluminum phosphate coatings

ABSTRACT

Aluminophosphate compounds and compositions as can be used for substrate or composite films and coating to provide or enhance, without limitation, planarization, anti-biofouling and/or anti-microbial properties.

This application is a continuation of and claims priority benefit fromapplication Ser. No. 10/745,955 filed Dec. 23, 2003 now issuing as U.S.Pat. No. 7,311,944 on Dec. 25, 2007 and provisional application Ser.Nos. 60/436,063 and 60/436,066, each filed on Dec. 23, 2002 andincorporated herein by reference in its entirety; U.S. application Ser.No. 10/627,194 filed Jul. 23, 2003 from prior provisional applicationSer. No. 60/398,265 filed Jul. 24, 2002; U.S. application Ser. No.10/642,069 filed Aug. 14, 2003 from prior provisional application Ser.No. 60/403,470 filed Aug. 14, 2002; U.S. application Ser. No. 10/362,869filed Feb. 21, 2003 from prior PCT application no. PCT/US01/41790 filedAug. 20, 2001; and U.S. application Ser. No. 10/266,832 filed Oct. 8,2002 as a continuation of application Ser. No. 09/644,495 filed Aug. 23,2000 and issued as U.S. Pat. No. 6,461,415 on Oct. 8, 2002—each of whichis incorporated herein by reference in its entirety.

The United States government has certain rights to this inventionpursuant to Grant Nos. F49620-00-C-0022 and F49620-01-C-0014 from AFOSR(Air Force Office of Scientific Research) and DE-FG02-01ER83149, fromthe Department of Energy each to Applied Thin Films, Inc.

FIELD OF THE INVENTION

The present invention relates to modification of metal and alloy,ceramic, and glass surfaces with an inorganic coating to provideplanarization, oxidation and corrosion protection of the coatedsurfaces. This invention is also related to the coating on solidsupports (e.g., glass) providing one or more reactive sites for theattachment of organic or inorganic molecules including but not limitedto aliphatic acids, organosilanes and biomolecules such asoligonucleotides. Stable molecular attachment can provide severaldesired mechanical, optical (second harmonic generation, fluorescenceand like), hydrophobic, hydrophilic, tribological, biological(antimicrobial) and other properties to the solid supports coated withthe inventive material. This invention is also related to chemicallymodifying the inventive material composition to impart useful propertiessuch as antimicrobial property.

BACKGROUND OF THE INVENTION

Advanced alloys, including nickel-based superalloys, intermetallics oftitanium-aluminum, niobium-aluminum, titanium-silicon,molybdenum-silicon-boron and others are used extensively for hightemperature applications due to their desirable mechanical properties.However, their environmental durability in oxidizing or harshenvironments is limited and various surface modification techniques,including protective coatings are employed to extend their lifetimesand/or use temperatures. Due to presence of surface pits, scratches,pores, or other abnormal surface features (more commonly known aspitting or crevice corrosion), accelerated oxidation or corrosion isinitiated in these areas which eventually degrades the entire surface.If the surfaces are prepared adequately, advanced alloys, that containaluminum for example, will form a uniform protective alumina scale whichlimits further oxidation. However, if the thermally grown scale is notuniform or contain other oxides, besides that of aluminum, theprotection is compromised and the alloys are subject to rapiddegradation at elevated temperatures. In addition, surface grainboundary junctions are compositionally different compared to the bulkcomposition which may also cause the oxide scale in those regions to bedifferent and perhaps less protective. Therefore, there is a need for asuitable surface modification method that will allow for the slow andsteady formation of predominantly alumina-rich (more preferably purealumina scale) scale for aluminum-containing alloys.

Similar arguments are valid for chromium-based steels and otherchromium-based alloys which are used in applications for boilers, heatexchangers, recuperators, interconnect for solid oxide fuel cells,automotive catalytic converters, and others as apparent to those skilledin the art. In these applications, it is desired to form a protectivechromia scale which requires a minimum level of chromium content in thealloy. Higher chromium content makes the alloy more expensive and alsoresults in compromise of other important mechanical, thermal, andelectrical properties of alloys. Thus, there is a need for a protectivecoating for chromium-based alloys and steels which will allow for theformation of a dense and uniform protective scale of chromium oxide,especially if it can be implemented for low chromium-containing alloys.

Metal or alloy honeycomb structures are used in many applications suchas catalytic converters, radiators and heat exchangers, and exteriorbodies of space vehicles for thermal protection. U.S. Pat. Nos.5,411,711 and 5,146,743, among others, discuss the metal foil catalyticconverters for automotive systems. Currently, most catalytic convertersused in automotive exhaust systems in the US use a ceramic honeycombsubstrate loaded with a precious metal catalyst. The ceramic honeycombis used because it can tolerate the hot exhaust environment withoutdegradation. Alloy foil honeycombs offer advantages over ceramichoneycombs in weight and electrical conductivity. Most auto pollutionoccurs when the engine is cold, generally after the engine is started.At low temperatures the catalysts are not effective at reducing nitrogenand oxidizing residual hydrocarbons. To alleviate this problem andachieve overall reduced emissions, alloy foil catalytic converters canbe resistively heated to ensure that the catalysts are kept at atemperature that allows them to function optimally. However, these thinfoils are prone to oxidation and corrosion in the exhaust stream. Foilsare particularly sensitive to oxidation because the original alloy is sothin, that the buildup of a thick oxide scale results in dimensionalchanges and changes in mechanical properties. For this reason, expensiveoxidation resistant alloys are required. A thin oxidation resistantcoating that will not substantially increase the thickness of the foilwill be useful to reduce oxidation and corrosion, allowing the use ofless expensive alloys, while still allowing the use of resistive heatingto reduce emissions. Another such application is the potential use ofalloy foils is for thermal protection systems for next-generationreusable launch vehicles for space travel. Present inventive materialcan be used as the oxidation protection coatings for these applications.

Currently, there are many ways to combat corrosion of aluminum andferrous alloys. They include painting, electroplating, compositecoverings, use of more corrosion resistant alloys, anodizing andchromating the surfaces of metal. Many of these processes are notenvironmentally friendly, cannot be maintained or repaired in the field,are expensive, require significant preparation of the substrate, andnone offer the required long-term, low maintenance protection. Pastcoating efforts have primarily used relatively thick coatings (1-20 milsthick) to combat salt corrosion. Anodizing of aluminum and chromateconversion coating of aluminum and ferrous alloys are the most effectivetechnologies, but both are environmentally unfriendly and require theuse of toxic chemicals. Corrosion often occurs in areas of surfacedefects of the alloy substrate. Pits and inhomogeneities in the alloycomposition cause accelerated corrosion. High strength aluminum alloysin particular are subject to pitting corrosion because of the influenceof Cu-containing intermetallic particles. The inhomogeneous distributionof Cu in the alloy microstructure has been shown to be a major cause forlow resistance to pitting or stress corrosion cracking. Heterogeneousmicrostructures are intentionally developed in commercial aluminumalloys to optimize mechanical properties. Unfortunately, suchmicrostructures make aluminum alloys susceptible to localized corrosionduring service and complicate aqueous surface finishing processes. Thestandard coating system uses a chromate conversion layer covered byorganic paints. Short term corrosion protection of metals and alloysfrom corrosion due to moisture and other environmental factors iscurrently achieved using organic layers. Time-consuming and arduous,these organic coatings need to be removed before the processing ofmetals and alloys like heating or melting or for painting and othersurface modifications.

Many metals, alloys and ceramics used in various applications require asmooth surface finish which is often accomplished by mechanical orchemical mechanical polishing means. In addition to passivation ofcoated surfaces, it is also desired to protect them from anyenvironmental attack during processing or surface modification or duringservice. Typically, anodization of the surface with the formation of analumina or chromia film is done to passivate the surfaces. However, theaforementioned procedures are expensive, labor intensive, and areenvironmentally unsafe releasing toxic substances and generating toxicwaste.

Physical vapor deposition (PVD) grown amorphous silicon nitride film onmetallic substrates are used for growth of single crystal magnesiumoxide films using ion-beam assisted deposition (IBAD) whereby the growthis induced by e-beam evaporation, sputtering or other PVD method withanother ion-beam to induce crystallographic alignment. Using thistechnique, biaxial texture of magnesium oxide is attained overthicknesses within 100 Angstroms as opposed to direct IBAD growth ofyttria stabilized zirconia (YSZ) on highly polished polycrystallinemetal or alloy substrates (hereafter referred to as metal substrates)which required growing much thicker films (over 1000 Angstroms) toattain similar quality biaxial texture. The IBAD magnesium oxide filmsserved as good templates for further heteroepitaxial growth offunctional oxide films such as ferroelectrics, superconductors,piezoelectric films, or other electronic films of the like. Thus, theIBAD MgO approach served as a much faster and economical way ofproducing biaxially textured or single crystal films on polycrystallinemetal substrates with amorphous interlayers (also known as nucleation oradhesion layers).

It has been recently demonstrated that yttria served as a much betteramorphous template layer (grown by PVD) than silicon nitride on highlypolished metal/alloy substrates. Specifically, the yttria/IBAD MgOapproach was used to demonstrate the architecture for growth of highquality High Temperature Superconductor (HTS) films suitable as HTScoated conductors. Specific disadvantages of this approach include: anexpensive (vacuum deposition process) low deposition rate process isrequired for yttria amorphous layer formation, the use of thin yttrialayer is not an adequate diffusion barrier against diffusion of oxygenand other metals to diffuse into the superconducting layer; thus, aseparate diffusion barrier layer is still required (currently strontiumruthenate is being used as diffusion barrier), and prior to depositionof yttria, the substrate roughness needs to be tailored below 40angstroms (preferably below 10 Angstroms) through mechanical orelectrical polishing methods. Thus there is a need for an alternativematerial and associated thin film process (preferably non-vacuum,low-cost, and high deposition rate) to replace yttria and siliconnitride or other layers which is multifunctional and performs better andcan be deposited at lower costs using a simple deposition process.

Low friction surfaces are required for many applications, includingbearings, bearing races, and gears. Low friction surfaces can beimparted by depositing a low-friction material as a coating or reducingthe overall surface roughness of the substrate. Although surface finishof metallic and ceramic parts can be improved through mechanicalpolishing, pits and defects contained on the surface cannot beeffectively removed through any of the standard polishing techniques.Deposition of extremely thin amorphous films that exhibit low surfaceenergy and provide hermetic coverage with adequate thermal andmicrostructural stability can be beneficial in maintaining a lowfriction surface whereby the defects on the metal surfaces areeffectively sealed.

Biofouling of ship hulls is caused by microorganisms such as slime,algae and bacteria, and macroorganisms such as barnacles, mussels, clamsand oysters which adhere to the hull of the ship. Fouling increases dragon the hull, decreasing ship speed and often significantly reducing fueleconomy. One of the promising emerging technologies is the nontoxic“foul-release” coating. These coatings are based on the hypothesis thatin surfaces with the weakest attraction for bio-organisms, fouling willbe slow and likely to require the least amount of effort to release fromthe surface. Fouling organisms adhere to the surfaces by secretingproteinaceous adhesives. Materials with low surface energy will offerlow adhesion strength, resulting in poor attachment and easy to removefouling. The feasibility of this approach has been established byresearchers using fluorinated polymers, epoxy based and silicone-basedcoatings. These coatings did foul, but fouling bio-mass can be easilyremoved by fast-flowing water. However, these polymer-based coatingshave limited heat and UV light resistance. Therefore, an inorganiccoating with smooth and low friction surface properties are highlydesirable.

Microarrays are arrays of biomolecules such as oligonucleotides that arespatially arranged and stably attached to a surface of a solid support.Microarray technology is used for parallel analysis of genes in a largescale, and has emerged as the universal genetic analytical tool for usein a wide range of biomedical applications. Commercial production of DNAchips has been implemented by many companies while, in parallel, medicalresearchers report exciting advances across many disciplines within thefield of medicine. These developments in microarray technology offertremendous promise to solving long-standing problems in public healthworldwide and also provide new avenues to combat the more recent threatsof bioterrorism.

The starting point or the basic building block for producingbiomolecular microarrays is a suitable solid template surface (solidsupport material) upon which biological molecules can be anchored orimmobilized. Several patents have been issued on functionalizingsilicate glass and other surfaces. Numerous other surface coatings havealso been disclosed. Patents are also awarded for novel solid supports,e.g. aluminosilicate, for immobilizing nucleic acids. Characteristics ofDNA microarrays are determined by the surface properties such aschemical homogeneity, interaction between surface and bio-molecules,surface roughness, density of surface functionality, spacing betweensurface functional moieties, amenability to DNA hybridization, and soforth. While the current methods employ the use of soda-lime glasssubstrates, they are prone to degradation over the long term and thesurface chemistry is not tailored to allow for suitable organicattachments. An organic linker is used to attach the DNA or otherbiomolecule to the surface of the substrate. Polylysine is a coatingmaterial currently recommended and one of several used for glass slidepreparation, as known in the art. However, polylysine-coated glassslides suffer from poor stability, extended curing cycles, and poorreliability such that new surface methodologies are critically needed tosupport the rapidly growing field of microarray technology. For example,polylysine-coated slides need to be stored for 14 days after coating forcuring purposes and should be used within four months due to degradationfrom oxidation. Typically, in a batch of polylysine-coated slides,several are rejected because of non-uniformity or opacity. In addition,the hybridized microarrays cannot be stored over long time periods.Stability of polylysine coating under UV light is also a concern.

Many alternative coatings to replace polylysine are being investigatedincluding aminosilanes, epoxy derivatives, aldehydes, and others. Whileaminosilanes or their derivatives offer superior stability, their lowbinding capacity has been a problem. Many of these limitations stem fromthe lack of desirable inorganic surface chemistry for bonding withorganics. Organic groups functionalized on soda-lime glass surfaces arenot stable under even slightly harsh conditions or chemical treatmentsand will degrade over time. Organic molecules interact only weakly withsoda-lime-silica surfaces. Under humid or other conditions, sodium ionsdiffuse to the surface of the glass and interact with organic moleculesresulting in degradation. Borosilicate or aluminosilicate glasses havealso been proposed, but they do not offer the ideal surface chemistryfor organic absorption.

Disinfecting and antimicrobial chemicals are commonly employed toeradicate microbial growth and improve hygiene. The adhesion ofmicro-organisms to surfaces is influenced by the bio-adhesivecharacteristics of the fouling organism and surface properties, such asits chemical composition and physical characteristics of the surfaceslike surface roughness. Fungi, such as molds, yeasts and algae arevisible in mass, but it can be advantageous to eliminate them earlier,when contamination and the consequential substrate deterioration has notyet become obvious. Highly active cleaning chemicals may be toxic andaggressive and, after repeated applications, degrade the surface andinactivate bioactive systems. Another major problem is the evolution ofmicrobial strains which are resistant to disinfectants and antimicrobialagents that are being used now. The issue of hygiene is especiallycritical to contact surfaces present in food processing, supply andcatering chains, health and medical establishments, animal husbandry,water and sewage operations as well as in heating, ventilation and airconditioning systems.

The performance factors of antimicrobial coatings include durability,retention of activity, and minimal degradation of surfacecharacteristics and appearance. The coatings must also show resistanceto heat, chemicals, solvents, staining, scratching, and moistenvironments. They should preferably be non-toxic, odorless, smooth,non-porous, easy or self clean, crack-free, avoid discoloration, havegood color retention and be UV resistant. Several potential noveltechniques are being developed to overcome these problems. These includealbumin affinity surfaces, surface modification with blue dextran,silver ion incorporation in a porous matrix, photocatalytic titaniumdioxide, silicone quarternary ammonium compounds and sacrificialcoatings that are alkali soluble or strippable and recyclable films. Amulti-layer film, fluoro/silicon containing resins, a dry paint filmwith additive coating or additives incorporated, the incorporation ofcleaning agent activators, the design of surface and cleansing system intandem, tuned ultraviolet, ultrasound and ozone could also be of value.

Among these antimicrobial techniques, there is a renewed interest insilver ion incorporation into coatings and substrates by researchers andcompanies. Several patents and publications have recently appeared onthe use silver ion incorporated substrates like zeolites, polymers,ceramic sheets and polyelectrolyte films. Silver compounds have beenexploited for their medicinal properties for centuries. It is aneffective agent with low toxicity. Although silver salts are effectiveantimicrobial agents, their use likely results in unwanted adsorption ofsilver ions in epidermis cells and sweat glands. To reduce thelikelihood of silver-ion adsorption into tissue, silver ions need to beincorporated into stable substrates.

The hydrophobic effect plays an important role in the defense againstpathogens. In addition to the unfavorable surface energy on thehydrophobic surfaces, microorganisms are also deprived of the waternecessary for germination and growth. Very few microorganisms are knownto survive in the absence of water. Hence, hydrophobic property impartedon inventive material coated surfaces may be regarded as the additionaldefense against microbes. The combined effect of both bactericidal andhydrophobic properties of inventive material coating will act as twolines of defense against harmful microorganisms. A hydrophobic layerwill prevent or reduce the adhesion of microbials and help in easycleaning. In case of damage occurring to this hydrophobic layer duringservice the antimicrobial agent loaded second layer will act as secondline of defense against microbes. Fiberglass insulation is usedextensively in building construction. Fiberglass is an effectiveinsulation, but is susceptible to moisture and can become a point forbacteria and mold to grow. Mold and bacteria growth in buildingmaterials causes indoor air pollution and can cause sickness in theinhabitants of the building. A water-repellent coating is desired tomaintain dry conditions of the fiberglass insulation. If the fiberglassis dry, then biological growth can be prevented. Therefore, thecombination of both hydrophobic and antibacterial property in oneembodiment will greatly help in situation like this and others.

SUMMARY OF THE INVENTION

In light of the foregoing, it is an object of the present invention toprovide aluminophosphate compounds, compositions and/or relatedcomposites or articles, together with methods for their use andpreparation, thereby overcoming various deficiencies and shortcomings ofthe prior art, including those outlined above. It will be understood bythose skilled in the art that one or more aspects of this invention canmeet certain objectives, while one or more other aspects can meetcertain other objectives. Each objective may not apply equally, in allits respects, to every aspect of this invention. As such, the followingobjects can be viewed in the alternative with respect to any one aspectof this invention.

For purposes of the present invention, the phrase “inventive material,”mention thereof or reference thereto will be understood to mean any ofthe present aluminophosphate compounds or compositions, over the entireavailable range of Al:P stoichiometries, as may be used in conjunctionwith a method, composite, or article of this invention, and/or a film,layer or coating associated therewith, or as otherwise provided below,such compounds or compositions prepared or characterized as describedherein, such compounds and compositions as may be alternativelyexpressed, respectively, as aluminum phosphate compounds andcompositions, and prepared, characterized and/or applied as described inU.S. Pat. Nos. 6,036,762 and 6,461,415 and co-pending application Ser.Nos. 10/627,194 and PCT/US03/36976, filed Jul. 24, 2003 and Nov. 19,2003, respectively, and 10/642,069 and PCT/US03/25542 filed Aug. 14,2003, each of which is incorporated herein by reference in its entirety.Without limitation, as described herein and/or through one or more ofthe aforementioned incorporated patents or applications, the inventivematerial can include such aluminophosphate compounds and compositionscomprising dopants, particles and/or inclusions of carbon, silicon,metals, metal oxides and/or other metal ions/salts—includingnonoxides—regardless of whether the aluminum content is stoichiometric,less than stoichiometric or greater than stoichiometric relative tophosphorous, on a molar basis. Embodiments of the inventive materialsare available under the Cerablak trademark from Applied Thin Films, Inc.

The inventive material comprises aluminophosphate and can be depositedas a thin film on substrates using a specially-designed precursorsolution that yields a unique form of amorphous aluminum phosphate. U.S.Pat. Nos. 6,036,762 and 6,461,415 issued to Sambasivan et. al and theabove-referenced patent applications provide details regarding theprecursor synthesis and chemistry, properties, and other processingdetails are provided. Various additions or modifications to surfacescoated with the inventive material are also considered embodiments ofthe present invention, examples of which are provided below.

One of the objects of the invention is to provide a method to depositthis inventive material coating as a thin, hermetic, microstructurallydense, uniform, and transparent coating using simple dip, spin, spray,brush or flow coating process. It is an object of the invention is touse inventive material coatings to passivate and protect metals andalloys from oxidation and corrosion during processing and service atroom and elevated temperatures. Another object of the invention is touse the present inventive material in conjunction with other coatingmaterials. For example, along with copper-chromium alloy coatings, theinventive material coating can be used to protect against oxidation ofadvanced copper-niobium alloys with less chromium content.

It is a further object of the invention to planarize metal and alloysurfaces such that the smoothness of the resulting surface is beneficialfor rendering a low-friction surface which should provide, for example,better wear characteristics. The planarized surface may also be suitablefor further deposition of other functional layer(s) above, over or ontop of the inventive material coating whereby the substrate is protectedduring processing of subsequent layers and the planarized surfaceprovides better quality overlayers. The smooth surface obtained due tothe planarization effect of the coating is also beneficial asfoul-release coatings for marine utilities.

Another object of the invention is that coatings of the inventivematerial applied to metal, alloys, ceramic or glass surfaces can beimparted with additional functions including but not limited tohydrophobic, hydrophilic, antimicrobial, optical, low-friction,anti-fouling, easy foul-releasing, mechanical and self-cleaningproperties by an additional layer of organic molecules. Such surfacemodification of metal and alloy, ceramics and glass surfaces with asubstantially pore-free and smooth inorganic film which is highly stableand with the additional organic layer make the surface multifunctionaland can provide a comprehensive method of protection and other broadrange of applications.

Another object of present invention is to preferentially attach orcouple biomolecules and other organic molecules to films or componentsof the inventive material, such molecules including, but not limited to,polypeptides, polynucleotides or nucleic acids onto inventive materialsurface, which is preferably obtained as a coating on a solid support.

It is another objective of this invention to tailor the inventivematerial coated surfaces with attachment of organic or inorganic orcombined molecules including, but not limited, to alkyl amines,carboxylic acids and organosilanes. It is another objective of thisinvention to use organic linker molecules attached to inventive materialsurface for biomolecular array preparation. It is another object of thisinvention to provide a mask layer over inventive material layer, whichcan be selectively removed chemically or photochemically. It is anotherobject of this invention to reduce or eliminate the fluorescenceimpurities present in the solid substrates which interfere in DNAhybridization analysis. It is another objective of this invention to useinventive material coating as barrier for interaction of attachedbiomolecules with detrimental species such as sodium ions present in thesubstrates like soda-lime glasses. It is another objective of thisinvention to tailor the hydrophobicity of the inventive material surfacecoated on solid substrates, for example, by selectively attachingsuitable organic molecules. This will help in processes such as DNAspotting from spreading. It is another objective of this invention tocoat the inventive material over silicon surfaces, thus allowing theintegration with DNA chip technology. It is another object of thisinvention to mass produce suitable solid supports to clean, consistentand durable solid supports for bimolecular array. It is another objectof this invention to attach functionally derivatized DNA molecules ontoinventive material surface coated over solid substrates. It is anotherobject of this invention to modify conventional solid substratesincluding but not limited to glass slides to be applied for preparingconsistent, clean, uniform, durable, and hard surfaces suitable formicroarrays.

Another object of present invention is to use inventive material as thesubstrate or carrier for organic and inorganic antimicrobial agents andin particular but not limited to silver ions. Antimicrobial agents canalso be incorporated within the inventive material matrix and used asantimicrobial powder.

Another object of the present invention is the development of alow-cost, durable, antimicrobial and corrosion resistant coatingmaterial in one embodiment. Another objective is the development ofsilver mixed-inventive material coated surfaces with additionalhydrophobic property through the attachment of a suitable organic layer.Yet another objective of the present invention is to use a porousoverlayer to the inventive material coating on substrates to impartlarge surface area to the surface for intake of higher quantity ofantimicrobial agents. The porous layer will be loaded with antimicrobialagents such as, but not limited, to silver ions. The porous layer canalso be functionalized by the uptake of selective organic compounds, forexample, adsorbed hinokitiol, tannin, lysozyme, protamine or sorbic acidthat can be released slowly for durable antimicrobial activity.

Other objects, features, benefits and advantages of the presentinvention will be apparent from this summary and its descriptions ofvarious embodiments, and will be readily apparent to those skilled inthe art having knowledge of various corrosion/oxidation protection,anti-microbial, anti-biofouling and bio-microarray coatings, filmsand/or applications. Such objects, features, benefits and advantageswill be apparent from the above as taken into conjunction with theaccompanying descriptions, examples, data, figures and all reasonableinferences to be drawn therefrom, alone or with consideration of thereferences incorporated herein. These and other objectives, advantages,and features of the invention will become apparent to those skilled inthe art upon reading the details of the invention as more fullydescribed below.

In accordance with the preceding and the inventive materials referencedabove and described elsewhere herein, the present invention is, in part,a method of using an aluminophosphate compound to decrease surfaceroughness. Such a method comprises (1) providing a precursor to analuminophosphate compound, the precursor comprising aluminum ions andphosphate esters in a fluid medium; (2) applying the precursor medium toa substrate having a first surface roughness value; and (3) treatingand/or heating the applied medium for a time and at a temperaturesufficient to provide a substantially amorphous aluminophosphatecompound on the substrate. Application and subsequent treatment of theprecursor medium, as described herein, as well as in the aforementionedincorporated references, provides a planarized substrate surface, suchplanarization as can be determined by a decreased, second roughnessvalue, as compared to the aforementioned first surface roughness value.Reference is made to several figures and supporting examples. Inpreferred embodiments, the surface roughness value can be decreased atleast by about a factor of 3. Alternatively, such a method can provide atreated substrate with a friction coefficient less than about 0.2.

A precursor to the aluminophosphate compound can be applied to thesubstrate using one or more techniques, as would be understood by thoseskilled in the art. Dip-coating can be used with good effect over arange of substrate materials and configurations. Spraying, flow-coatingand spin-coating can be used with comparable effect, depending uponchoice of substrate. Without limitation, a substrate used in conjunctionwith a method or composite of this invention can include a steel, anickel-based alloy, a superalloy, titanium, a titanium-based alloy,niobium, a niobium-based alloy, molybdenum, a molybdenum-based alloy,silicon, aluminum oxide, an enamel, mullite, a glass, fused silica, asilica-based refractory and a ceramic material. Likewise, for purposesof illustration and without limitation, such a substrate, in particularthose comprising a metal, alloy or ceramic material, can be configuredto provide a bearing, a gear, or a medical implant component.

Further demonstrating the utility of this invention, providing asuitable substrate, an aluminophosphate compound of this invention canhave deposited thereon a biaxially-textured component such as but notlimited to magnesium oxide, yttria and an yttria-stabilized zirconia.With such embodiments of the methodology and/or composites of thisinvention, a lattice-matching and/or an electromagnetic component can bedeposited on such a textured component. As would be understood by thoseskilled in the art made aware of this invention, such an electromagneticcomponent can comprise a superconducting YBCO ceramic material.

In part, the present invention is also a composite comprising asubstrate, a substantially amorphous aluminophosphate compound and anorganic component attached to the aluminophosphate compound. Typically,the aluminophosphate compound is on the substrate, but can, optionally,be provided as an overlayer or coating on another component deposited onthe substrate. Regardless, as described elsewhere herein, the organiccomponent can comprise a compound having synthetic, clinical and/ordiagnostic application. Such a biomolecule can be selected from but isnot limited to a protein or an amino acid residue thereof, apolypeptide, a polynucleotide or a fragment, component or residuethereof. As discussed elsewhere herein, such a composite and associatedmethodology can be used for the coupling, attachment or bondinginteraction with a DNA fragment or component. Such coupling orattachment of the aluminophosphate compound with a particularbiomolecule can be direct or via a molecular linker component.Polylysine can be used as can other linker components known in the artto those individuals made aware of this invention, such componentsincluding a range of organosilane compounds. Examples of the latterinclude difunctional aminosilane compounds which can be used for thecoupling or attachment of the range of biomolecules, directly or by wayof synthetic modification, to the aluminophosphate compounds orcompositions of this invention.

In part, the present invention can also include a substantiallyamorphous composition comprising an aluminophosphate compound and anantimicrobial component. Without limitation, the antimicrobial componentcan be selected from silver, copper, zinc and iron ions. Regardless,such an antimicrobial component can be incorporated into such acomposition over a range of effective concentrations. However, dependingupon desired effect, the ratio of antimicrobial to aluminophosphatecomponent can range from about 0.1:1 to about 1:1. As describedelsewhere herein, such a composition can be applied or deposited on asubstrate, such a composite can further comprise one or more organiccomponents to provide additional functional effect. Without limitation,such an organic component can be selected from a fatty acid or a silanecompound to provide enhanced hydrophopicity. Alternatively, enhancedeffect can be achieved through choice of an appropriate detergent orsurfactant component, with incorporation of the metal cations to provideantimicrobial effect and the organic anion to enhance hydrophopicity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Schematic figure showing the ability of the microstructurallydense and hermetic inventive material coating to seal off surfacedefects and grain boundaries on a metal or alloy specimen. (a) indicatesa grain boundary, (b) indicates a pit and (c) indicates a scratch in thesurface. The inventive material coating effectively seals such defects.

FIG. 2. Schematics showing typical architecture to develop HTS films ona metal substrate. The respective layers are (a) polycrystalline metalor alloy substrate, including but not limited to Inconel, stainlesssteel, 1-624, and nickel chromium alloys, (b) an inventive materialcoating, for passivating and planarizing the substrate, (c) IBAD MgO orYSZ, (d) homoepitaxial MgO or YSZ, (e) CeO₂ and (f) HTS layer. FIG. 2Ashows how the inventive material can be used in the currentarchitecture. FIG. 2B shows how the inventive material can be used toreduce or eliminate the need for the diffusion layer (d).

FIG. 3. Schematic showing the immobilization of biomolecules oninventive material coated on solid substrates.

FIG. 4. Cross-sectional transmission electron micrograph showing awell-adherent, thin, uniform, dense and hermetic film of the inventivematerial deposited on the 304 stainless steel.

FIG. 5. Photograph of coated and uncoated Ti-46 alloy after 100 hours ofexposure at 800° C. in ambient air showing the oxidation protectionability of the inventive material.

FIG. 6. Photograph of uncoated and coated nickel rods exposed at 550° C.for 115 hours in ambient air. Higher reflectivity for the coated nickelrelative to uncoated sample is readily apparent. A coating of theinventive material not only provides the desired oxidation protection,but the hermetic nature of the coating also provides protection of thesubstrate from environmental attack during service from variouscontaminants in the atmosphere such as sulfur, chlorine, acids, salt,and moisture.

FIG. 7. Schematic showing the planarization effect of a coating of theinventive material on relatively rough surfaces.

FIG. 8. Comparative photographs showing antimicrobial susceptibilitytest with e. coli, bacterial growth inhibition (A) a slide coated withan inventive material comprising silver ions and (B) ‘control’ sample,glass slide coated with inventive material and not loaded withantimicrobial silver ions.

FIG. 9. Grazing angle Fourier Transform Infrared reflectance spectrum ofan embodiment of the inventive material coated on a stainless steelsample and cured at 500° C. for 5 minutes.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

As mentioned above, the present invention relates to an aluminophosphatecompound/composition with a variable aluminum to phosphorus ratio whichis stable to high temperature. Without limitation, the molar ratio ofaluminum to phosphorus can range from about 0.5:1 to about 10:1,preferably ranging from about 1:1 to about 4:1, most preferably rangingfrom about 1:1 to about 2:1. Films, layers and/or components of theinventive material are available using an inexpensive chemical precursorsolution that deposits a uniform, hermetic, transparent thin film by asimple dip, paint, spray or flow coating process, such precursor(s) andmethods of deposit as are more fully described in the aforementionedpatent and application references.

Present inventive material offers a) excellent protection againstoxidation, b) the formation of stable protective oxide scales, and c)adequate sealing of defects (such as pits) on alloy surfaces such thataccelerated oxidation is prevented during the early stages of exposure(see FIG. 1 for a schematic representation of the effect of inventivematerial coating metal and alloy substrates). Among these, the mostrelevant and innovative attribute, without wishing to be bound bytheory, is the ability of the inventive material to promote formation ofa dense, continuous and protective oxide scale underneath during earlystages of oxidation. It is apparent from studies on stainless steel thata dense chromia-rich scale is formed preferentially in coated materialscompared to a highly porous iron-rich scale for uncoated specimens. Inthe latter case, extensive oxidation is observed with subsequentspallation of the scales. An order of magnitude difference in oxidescale thickness was observed between coated and uncoated AUS 304substrate coupons.

Inventive material coatings on nickel-based superalloys and titaniumalloys may extend turbine lifetimes, limit failure, and allow higheroperational temperatures with minimal additional cost. Inventivematerial coating on alloy foils reduces oxidation and corrosion whichmay find application with metal foil catalytic converters. In addition,a component (e.g., a film) of the inventive material may be used toprotect other alloy and metal specimens from oxidation and corrosion.The coating process is simple, scalable, and amenable to field repair.Protection from oxidation at elevated temperatures has been demonstratedfor a number of alloy substrates including titanium alloys, nickel-basedalloys, steel, cast iron, and inconel.

In addition to protecting alloys from oxidation during serviceconditions, the present inventive material can be used to protect alloysfrom oxidation during hot forming. Metals and alloys are sometimesheated (strengthening or case hardening) for forming to produce aspecific shape for future use. The mechanism of protection is the sameas protection at use conditions, although the heat treatment isrelatively short (a few minutes to hours), and the coated alloy may ormay not be intended for use at high temperature.

In addition to depositing the coating using a clear precursor solution,powders can be made and dispersed in the solution to form a slurrycoating. The coating is then applied in the same manner as the clearsolution. Powders can also be thermal sprayed onto a substrate. Black,gray color of various shades or white powders of the inventive materialcan be used as pigments and dispersed in a paint medium and used incoating surfaces.

The inventive material coating can be used as part of a multilayeredcoating system. Coatings of other compositions can be deposited eitherunderneath or over the inventive material coating. One example of thisembodiment of the invention is the use of inventive material coating asan oxidation barrier between an alloy substrate and a thermal barriercoating. Thermal barrier coatings are used to reduce the temperature ofan alloy substrate, but do not offer significant oxidation protection. Acomponent coating of the inventive material can be applied underneaththe thermal barrier coating to reduce oxidation of the substrate.

The inventive material can be used as multilayers to tailor desiredproperties with varying chemistries or microstructrures in each layer toform a functionally-graded structure or to produce thicker layers toincrease the protection ability against corrosion and anti-tarnishing.The inventive material coating can be used to retain or improve the heatand light reflectivity of coated surfaces substantially at low as wellas elevated temperatures.

The planarization induced by inventive material will be useful for anumber of applications including those requiring wear resistance or lowfriction surfaces. In addition, the smooth amorphous surface can alsoserve as a template (due to better adhesion characteristics withdeposited overlayers of organic or polymeric or ceramic materials) forgrowth of additional layers for adding functionality. For example,amorphous template layers are desired for growth of textured films forelectronic applications. In particular, growth of biaxially texturedsuperconductor films is desired for long length high temperaturesuperconducting (HTS) tapes. Several patents have been issued related tousing ion beam assisted deposition (IBAD) to create a biaxially texturedoxide template on metal/alloy or amorphous (silica/Si) substrates,including U.S. Pat. Nos. 6,383,989 and 6,312,819, each of which isincorporated herein by reference.

Presently, both silicon nitride and yttria are used as amorphous“nucleation” or “adhesion” in the IBAD or Inclined Substrate Deposition(ISD) approaches. Thus, there is a need for an alternative material andassociated thin film process (preferably non-vacuum, low-cost, and highdeposition rate) to replace yttria and silicon nitride or other layerswhich is multifunctional and performs better and can be deposited atreduced costs. Inventive material produced using a dip-coating or othersolution-based process offers an excellent opportunity to replaceexisting amorphous template technologies for IBAD film growth. By asimple dip-coating process, the inventive material can be deposited as amicrostructurally dense, hermetic, thin (50 nm-1 μm), pin-hole free,uniform, and smooth film at relatively high rates in one pass. Theinventive material coating is a better alternative because of the lowcost coating process, high throughput, thermally stable and durablenature of the coating, and will provide excellent protection tosubstrate, but may also be suitable for etching to pattern thesemiconductor layers for solar array applications.

Inventive material coatings suitable as an IBAD template layer haveseveral advantages over current technology. As a hermetic coating, theinventive material seals off pits, scratches, and other defectstypically found even on well-polished substrates which can becorrosion-active and may affect the texture quality of IBAD film inthose areas. Deposition of inventive material on metal or alloy orceramic surfaces also induces a planarizing or smoothening effect sothat the surface roughness can be significantly reduced which may allowfor reduced polishing effort. Inventive material is a highly inert andstable high temperature material with low oxygen diffusivity. Thediffusion barrier characteristics are very important so that diffusionof metal species into the functional oxide layer is limited during hightemperature growth of the oxide layer. Typically, the multilayer stackwill contain a buffer layer on top of the IBAD layer to preventdiffusion of metal species into the functional layer (See FIG. 2, forthe schematics showing typical architecture to develop HTS films on ametal substrate).

Thus, the inventive material can serve as an excellent template for IBADgrowth for a number of applications including, but not limited to, HTScoated conductors, ferroelectrics, piezoelectrics, optoelectronics orelectro-optics. It also has a low dielectric constant so that it can beintegrated easily into silicon-based technology and used as a gatedielectric layer for silicon-based semiconductors. Biaxially textured orsingle crystal films of piezoelectric ceramics are being targeted foradaptive and flexible structures for aerospace and other applications.The inventive material deposited on flexible metal/alloy foil substrateswill offer corrosion and oxidation resistance while serving as a stableand inert template for IBAD growth of piezoelectric films, thus creatinga stable adaptive wing or other structures with high electromechanicalcoupling (due to high quality texture) produced at much lower costs ascompared to current methods. The IBAD process can also be used toproduce single crystal or biaxially textured films on flexible metalfoil substrates suitable for solar cell applications. Single crystalgermanium and GaAs layers are desired on metal foil substrates for solararrays. The current approach is to use polycrystalline semiconductorlayers on metal or polymer substrates, limiting the solar conversionefficiencies. The IBAD approach may be ideally suited to producetextured layers.

Growth of epitaxial conductive oxide electrode layers is desired onamorphous substrates (such as ruthenium oxide) for use in actuators andother devices; inventive material can serve as an excellent template onsilicon. Although thermally grown silica films on silicon may besuitable for the same purpose, growing a 100 nm silica scale on siliconby thermal oxidation require very high temperature processing and longscale formation times which also induces stresses so that themicrostructure and morphology of the oxide scale is not optimal forsubsequent growth of oxides. With the inventive material, at a lowdeposition temperature, a nominal 100 nm thick film, which is uniform,hermetic, and dense can be grown within few minutes by curing above350-500° C.

Planarization can be induced on relatively rough surfaces by depositingmultiple layers of coatings of the inventive material, where eachcoating has a lower surface roughness than the coating underneath.Coatings of the inventive material were deposited on 4340 steel couponsand the friction coefficient was found to be ˜0.1-0.14. In addition tothe low friction properties, the inventive material has a low surfaceenergy of 32 dyne/cm. With organic molecules attached to the inventivematerial surface, the surface energy can be lowered even further.

The surface of inventive material coatings can be further tailored bythe purposeful deposition of organic overlayers. The use of functionalorganic overlayers on metal or alloy substrates has many applications,including but not limited to the use of organic catalysts on metalreactor vessels. Without wishing to bound by any theory the adsorptionof organics may result from the presence of active adsorption sites onthe inventive material surface. These active organic attachment sitesmay be attributed to the presence of unsaturated aluminum ions (bondedto three or less oxygen atoms) or P doublebond 0 moieties (P═O), orAl—OH and/or P—OH groups on the surface of the inventive material.Further Al—O—Al and A—O—P bridging groups, present on the surfaceresulting from the pyrolysis of the precursor solution can also renderthe inventive material highly reactive. Molecular water, alcohol,acetone or ether can dissociatively adsorb on these sites uponatmospheric exposure resulting in reactive Al—OH and P—OH groups. Thesereactive hydroxyl groups can also be formed on the inventive materialsurface purposely by treating with dilute acid or other chemical methodsthat are familiar to those skilled in art. The organic attachment isvery stable and durable toward subsequent chemical, thermal, andmechanical treatments

Thus, the inventive material offers a new and unique glass surfacechemistry which has tremendous promise for use in biomoleculeimmobilization. The attractive attributes of inventive material includethe nature of the glassy material and the simple dip coating processused to develop a thin, uniform, dense, hermetic, and transparent film(see FIG. 3, for a schematic representation of microarray usinginventive material coated substrates). The coating also provides thebenefit to seal off any surface flaws or defects, thus providing a veryuniform and consistent surface chemistry which is essential formicroarray and other biotechnological applications.

Another aspect of this invention is the preservation of an inorganicsurface prior to biomolecular deposition. Normal procedures for usingsoda lime glasses include extensive cleaning and inspection of surfacesto ensure scratch and contaminant-free surfaces prior to polylysinedeposition. These procedures are tedious and time-consuming and areprone to manual errors and can cause unknown failures on precious DNAsamples and hence raises concern with the current approach. Incomparison, immediately after forming inventive material coatings, theycan be masked with a surfactant layer which may include but is notlimited to oleic acid layers, which provide excellent coverage and ahydrophobic surface which repels water and other contaminants (non-stickcoating). These masked layers can be easily removed just prior toorganic deposition such that a pristine surface of the inventivematerial is exposed for producing consistent and high quality organic orbiomolecular overlayers. Such an approach cannot be used to protectsodalime glasses since the bonding with organics is fairly weak andsurfaces tend to get hydroxylated to form silanol groups as opposed toorganic adsorption. High quality coatings of the inventive material withorganic layers on glass can also provide self-cleaning glass productssuited for architectural windows and automotive applications.

Two other alternative approaches are possible for attachment ofbiomolecules on an inventive material surface. One method involvesdeveloping a suitable organic anchor layer which has functional groupsfor subsequent bonding with DNA or other biomolecules. The coupling,attachment and/or bonding of the organic layer with an inventivematerial coating is fairly robust as it can be tailored with acarboxylic or amino terminating groups. A second alternative is to usethe inventive material as a stable buffer layer for use in conjunctionwith linker molecules, compounds or moieties including thecurrently-used polylysine-based coating systems. Thecompounds/compositions offer important benefits of this inventioncompared to the current system via providing a chemically inert surface,strong bonding with polylysine, and superior surface morphology notlimited to smooth, dense, and nearly defect-free surface.

The inventive material and/or precursor solution with metal cationsincluding, but not limited to silver, copper and zinc can be used inantimicrobial coatings. Inventive material mixed with antimicrobialagents coated surface can act as antimicrobial on contact. Organicantimicrobial agents can also be attached onto the inventive materialsurface owing to the strong and unique affinity of inventive materialfor organic molecules. Antimicrobial agents not limited to antimicrobialsurfactants can also be adsorbed on to surfaces coated with inventivematerial. These will act both as antimicrobial and hydrophobic surfaces.End groups of surfactants can be alkyl, or trifluoro alkyl groups.Trifluoro end groups are preferred for higher hydrophobicity. Dryconditions because of a hydrophobic surface will help in preventingmicrobial growth. Metal cation salts of surfactants not limited tosilver salts of acid surfactants (e.g. silver salt of oleic acid) canalso be used as the adsorption layer on the inventive material coatingto enhance the antimicrobial activity. Not wishing to be bound by anytheory, it is believed that the carboxyl group is attached to aluminumcation and silver ion to phosphate group. Since the inventive materialcan be coated by a simple process, and not limited to dip coating, on avariety of substrates, several fields of applications can be exploited.Applications of antimicrobial coatings are listed in Table 1. These areonly representative examples and not exhaustive list of potentialapplications of the present invention.

TABLE 1 Property Substrates Applications Antimicrobial, Glass Windows,Cell Cultures, Anchoring substrate Micro array Protein adsorptionAntimicrobial, and Steel Building Construction corrosion (push-plates,kick-plates, towel dispensers, escalators, door knobs, light fixtures,bath room components, Air- handling duct systems) Antimicrobial AluminumServing trays, salad bars, Refrigerators, Coolers, Food packaging.Antimicrobial Floor Tiles Serving counters, food preparation surfaces,animal shelters Antimicrobial Ti and Ti- Surgical instruments, basedalloys, Catheters, Guidewires, Stainless Introducers, Shunts, Tubes,steel, Endoscopes, Blades, Needles, Platinum, Coiling wire, PTCAstylets, Nitinol Mandrel wire Microbially Marine/ Against growth ofbacteria, Influenced Corrosion Aquaculture algae, fungus, mold, and (&salt corrosion) mildew under water (swimming pool)

For some applications, it is possible to tailor the inventive materialcomposition to alter its mechanical (nanocomposite films), thermal(improve conductivity through inclusions), electrical (add cationicsolutions to precursor to improve electrical conductivity), optical,chemical properties, and biological properties (antimicrobial) thusenhancing the product capabilities and performance. In the case ofmetallic surfaces, bioactive inventive material surfaces can serve dualpurpose: corrosion resistance and antimicrobial coating. Suchmultifunctional coatings are highly desired. Other approaches includeforming a porous layer of aluminum phosphate layer over a hermeticcoating of the inventive material. The porous layer can be loaded with adesired amount of antimicrobial agents including, but not limited to,organic antimicrobial agents such as hinokitiol, tannin, lysozyme,protamine and sorbic acid and inorganic ions such as silver, copper orzinc. These agents can be released slowly for antimicrobial activity.Silver ion embedded in an inventive material coating on glass substrateshowed antibacterial activity against E. coli bacteria preventing thegrowth of the bacteria around the coated glass surface. This propertycan be exploited in destroying microbes or preventing the growththereof.

EXAMPLES OF THE INVENTION

The following non-limiting examples and data illustrate various aspectsand features relating to the compounds, compositions, composites,articles and/or methods of the present invention. In comparison with theprior art, the present compounds, compositions and/or methods provideresults and data which are surprising, unexpected and contrary thereto.While the utility of this invention is illustrated through the use ofseveral aluminophosphate compounds/compositions and films/coatingsthereof, it will be understood by those skilled in the art thatcomparable results are obtainable with various other compounds,compositions and stoichiometries, as are commensurate with the scope ofthis invention.

Example 1

A preferred method for depositing a component film/coating of theinventive material coating is with a clear chemical precursor solution,with the solution preferably containing an aluminum salt and phosphateesters in an organic solvent. A solution used to deposit inventivematerial coatings with a 2 to 1 molar ratio of aluminum to phosphorus ismade by dissolving 264 g of Al(NO₃)₃.9H₂O in 300 mL ethanol. In aseparate container, 25 g P₂O₅ is dissolved in 100 mL ethanol. Thesesolutions are mixed together. The resulting solution is diluted withethanol to a concentration of about 0.2 moles Al/L solution.

Example 2

1″×2″ 304 stainless steel foil is coated with the precursor solution ofExample 1. The sample is heated at 500° C. for 15 minutes in a preheatedfurnace. A small part of this heat treated sample is prepared fortransmission electron microscopic study of cross section of theinventive material coating on the substrate. FIG. 4 shows the thicknessof the coating to be about 100 nm. The inventive material coating iswell-adhered to the stainless steel surface, and the micrographdemonstrates the continuous, dense and hermetic nature of the coating.

Example 3

Titanium-based alloys tend to oxidize readily, causing changes in thedesired properties of the alloy. Titanium can be alloyed with otherelements (aluminum, for example) to increase oxidation resistance, butmechanical properties may suffer. An ultra-thin coating which canprotect titanium alloys from oxidation is greatly desired. The inventivematerial has been shown to protect titanium aluminide alloys fromoxidation. The solution described in Example 1 is deposited on a Ti-46Alcoupon and cured by heating at 600° C. for 2 minutes. Samples coated bythis method were exposed to 800° C. in ambient air for 100 hours, alongwith an uncoated sample. The weight change from oxidation wassignificantly lower for the coated specimens. FIG. 5 shows a photographof coated and uncoated samples after the test.

Weight change after 800° C., 100 hour exposure in ambient air (mg/cm²)

coated sample 1 0.000034

coated sample 2 0.000033

uncoated sample 0.017

Example 4

A coupon of Ti-6Al-4V was dipped into a chemical precursor solution asdescribed in Example 1. The coating was dried with cool air and heattreated at 600° C. for 2 minutes in a preheated furnace. The couponswere then exposed to ambient air at 800° C. for 100 hours. The weightchange from oxidation was orders of magnitude lower for the coatedspecimen.

Weight change after 800° C., 100 hour exposure in ambient air (mg/cm²)

coated sample 0.000077uncoated sample 0.027

Example 5

Oxidation protection of nickel has been demonstrated with a film/coatingcomponent of the inventive material. The coating will help passivate thenickel or nickel alloy substrate such that protection against hightemperature oxidation or protection against corrosive environments suchas salty or sulfur or chlorine-containing atmospheres, is imparted. Anickel rod was dipped into a chemical precursor solution as described inExample 1 and dried in flowing air. The coated rod, along with anuncoated control specimen, was annealed in ambient air at 550° C. for115 hours. The uncoated sample showed a dark oxide film, while thecoated sample retained the metallic luster of the original rod (FIG. 4).

Example 6

Metal and alloy surfaces have varying surface finishes and roughnessdepending on the desired application, cost of preparation and otherfactors. Many metal and alloy surfaces are grit-blasted before coatingto clean off prior surface preparations or existing corrosion residues.A coupon of type 304 stainless steel is grit blasted to give a roughsurface finish. The solution described in Example 1 is deposited on thesurface through dip coating. The coating is dried in flowing air andcured with an IR lamp for 5 minutes. Optical microscopy showed that thecoating substantially covers the sample and is essentially crack-free.The coupon of annealed, along with an uncoated coupon at 1100° C. for 4hours in a furnace. The coated coupon shows significantly less weightgain from oxidation than the uncoated coupon.

Weight change after 1100° C., 4 hour exposure in ambient air (mg/cm²)

Coated sample 6.52Uncoated sample 26.34

Example 7

The inventive material can be used to planarize or smoothen a variety ofsubstrates. The solution of Example 1 is deposited on an alloysubstrate. Atomic force microscopic measurements were performed oncoated and uncoated samples to determine the root mean square (rms)roughness. The uncoated alloy has a rms roughness of 21 nm. The rmsroughness decreases to 7 nm upon application of the coating.

Example 8

Inventive material coatings on metal and silicon substrates can be usedfor subsequent growth of epitaxial layers for electronic applications.Specifically, this example relates to use of inventive material coatingas a template layer for producing high current carrying high temperaturesuperconducting (HTS) tapes. A piece of C-276 nickel-base alloy orHastelloy foil having an initial “as-received” rms roughness of 570 Å isdipped in the solution of Example 1. The coated foil is dried in flowingair and heat treated at 570° C. for 1 minute in a preheated furnace. Therms roughness is reduced to below 140 Å for a nominal thickness of 100nm for the inventive material coating. FIG. 7 shows a schematic of theplanarized surface.

Example 9

Using an ion-beam assisted electron beam deposition process, a thinoxide of yttria stabilized zirconia (YSZ) (thickness ranging from 50-100nm) with substantial biaxial texture is grown on the surface of theinventive material coating of Example 7. A thin cerium oxide layer(10-20 nm) with substantial biaxial texture is grown on top of YSZ toprovide a lattice-matching template for subsequent growth of 1-2 μm hightemperature superconducting YBCO film by electron beam deposition. Theentire multilayer stack represents a HTS coated conductor architecturewhich can be produced in long lengths.

Example 10

Inventive material coated substrate of Example 7 is used to deposit a100 Å layer of MgO using ion-beam assisted e-beam deposition processwhich has substantial biaxial texture. Subsequent layers of cerium oxideand YBCO films are deposited as described in Example 8. Note that theinventive material coating is serving both as a adhesion/planarizationlayer as well as an effective diffusion barrier. Thus, a separatediffusion barrier layer of YSZ or other oxide may not be necessary toavoid diffusion of species from substrate into YBCO that will degradesuperconducting properties. With this architecture, the YBCO layer willhave substantially improved texture and uniformly textured over largeareas and will carry high critical current densities as desired inrelated HTS applications.

In another embodiment of this example, a multilayer coating of inventivematerial can be deposited with varying aluminum to phosphorous ratiossuch that the adhesion is further improved and the planarization isfurther improved. These improvements will result in a more mechanicallyrobust HTS coated conductor with consistent properties over longlengths.

In yet another embodiment of this example, the same procedure describedherein can be followed to develop a stack using silicon as a substrate.Inventive material coated silicon substrates can be used as templatesfor growth of IBAD YSZ or MgO layers with substantial biaxial texture.These epitaxial layers can then serve as templates for further growth ofHTS, ferroelectric, piezoelectric, or other functional layers comprisingof oxides with cubic symmetry. The inventive material layers can alsoserve as dielectric layers for silicon-based devices.

In yet another embodiment of this example, the as-received substratewith rms roughness values of about 570 Å is mechanically polished, usinga lapping technique, to reduce the roughness value to below about 400 Å,more preferably below about 300 Å and most preferably below about 200 Åand then the inventive material coating (about 100 nm thick) isdeposited (either as a single layer or multiple layers) to furtherreduce the roughness below about 70 Å, preferably below 40 Å and morepreferably below about 20 Å and most preferably below about 10 Å. Thehighly smooth amorphous surfaces can then serve as templates for IBADgrowth of oxides using a physical vapor deposition technique.

Example 11

In addition to resistance to oxidation and corrosion at elevatedtemperatures, inventive material coatings can protect againstatmospheric corrosion at lower temperatures. Lab tests for saltcorrosion resistance are carried out in a salt fog chamber, according toASTM standard B 117. A coupon of aluminum alloy 6061 was dipped in thecomposition of Example 1 and retracted. The coupon was dried in flowingair and heat treated at 500° C. for 2 minutes. This coupon, along withan uncoated coupon was placed in a salt fog chamber for 170 hours. Thecoated coupon showed significantly less corrosion than the coated coupon(FIG. 7).

Example 12

Titania nanoparticles are know to exhibit desired optical or mechanicalproperties as a bulk material or when incorporated into a film. Atransparent host matrix for the titania nanoparticles is required iftransmission of light to the titania particles is desired. Titaniananoparticles can be produced in an inventive material precursorsolution by the addition of titanium isopropoxide solution. 4 mL oftitanium isopropoxide is added to 9.8 mL water and 0.2 mL nitric acid toproduce a solution with a cloudy appearance (partially hydrolyzed). Thissolution is added to the solution of Example 1 to produce a titaniacontaining precursor of the inventive material.

Example 13

A coating of an inventive material containing titania nanoparticles canbe deposited on a substrate, including but not limited to steel or glassor fused silica. A piece of 304 stainless steel is dipped in thesolution of Example 11 and removed. The coating is dried with cool airand heat treated to 800° C. for ½ hour. The resulting coating ishermetic and optically transparent.

Example 14

Zirconia inclusion in a film are desired to induce certain desirableoptical or mechanical properties. A nanocomposite of the inventivematerial and zirconia can also be made. 1.49 g ZrO(NO₃)₃.xH₂O wasdissolved in 10 mL of ethanol. In a separate beaker, 6.46 g P₂O₅ wasdissolved in 70 mL ethanol. In another beaker 59.9 g Al(NO₃)₃.9H₂O wasdissolved in 140 mL ethanol. All three solutions were mixed together andstirred. A clear solution resulted. The solution was dried at 150° C. ina convection oven to form a gel powder and annealed to 1000° C. for 1hour. Crystals of tetragonal ZrO₂ and predominately inventive materialwere identified by x-ray diffraction.

Example 15

A coating of the inventive material with zirconia nanoparticles isdeposited on 304 stainless steel by dipping in the solution of Example13. The coupon is dried in flowing air and heat treated to 800° C. for20 min to produce a nanocomposite coating.

Example 16

With reference to the precursor of Example 1, the ethanolic P₂O₅solution is added to the ethanolic nitrate solution. 0.1 g of AgNO₃solid is dissolved in 10 mL of the mixed solution.

Example 17

A coated glass specimen prepared with a treated aluminophosphatecompound of Example 16 is placed onto a Petri dish containing E. colibacterial strain. A control petri dish without the slide is alsoprepared. Both slides are kept at 35° C. for 2 days. After two days,silver/inventive material coated glass showed no bacterial growth aroundthe slide as compared to the control experiment showing the growth alongthe strain streaks

Example 18

A 1′×2″ stainless steel foil was dipped into the composition ofexample 1. The coupon was cured at 500° C. for 5 minutes in a preheatedfurnace. The resulting coating was highly reflective.

FIG. 9 shows the 80 Grazing angle FTIR spectrum of the cured stainlesssteel foil recorded using Perkin-Elmer Spectrum One FTIR spectrometer.Strong absorption peak centered near 1207 cm⁻¹ along with a broad peakcentered near 735 cm⁻¹ were observed. These peaks are due to phosphateand Al—O—P group vibrations. The peak near 830 cm⁻¹ is also observedwhich may be due to Al—O—Al bonding groups. Those skilled in the artwill understand that these peak positions can vary in the range 1280cm⁻¹-1180 cm⁻¹ and 860 cm⁻¹-700 cm⁻¹ depending on the curingtemperatures, composition of the precursor solution, coated substrateand other conditions. Peak intensities also can vary based on thecoating, curing and other conditions.

1. A method of using an aluminophosphate compound to decrease surfaceroughness, said method comprising: providing a precursor to analuminophosphate compound, said precursor comprising aluminum ions andphosphate esters in a fluid medium; applying said precursor medium to asubstrate, said substrate having a first surface roughness value; andtreating said applied medium for a time and at a temperature sufficientto provide a substantially amorphous aluminophosphate compound on saidsubstrate, wherein the surface of said substrate is planarized and has asecond roughness value decreased compared to said first surfaceroughness value.
 2. The method of claim 1 wherein said surface roughnessvalue is decreased at least by about 3-fold.
 3. The method of claim 1wherein said medium is applied by a process selected from dip-coating,spraying, flow-coating and spin-coating.
 4. The method of claim 1wherein said treated substrate has a friction coefficient less thanabout 0.2.
 5. The method of claim 4 wherein said substrate is selectedfrom a bearing and a gear.
 6. The method of claim 1 wherein abiaxially-textured component is deposited on said aluminophosphatecompound.
 7. The method of claim 6 wherein said component is selectedfrom magnesium oxide, yttria, and a yttria stabilized zirconia.
 8. Themethod of claim 7 wherein an electromagnetic component is deposited onsaid textured component.
 9. The method of claim 8 wherein saidelectromagnetic component is a superconducting YBCO layer.
 10. Themethod of claim 1 wherein said treated substrate is exposed to anenvironment inducing condition selected from oxidation and corrosion.11. The method of claim 1 wherein said substrate is selected from asteel, a nickel-based alloy, a superalloy, titanium, a titanium-basedalloy, niobium, a niobium-based alloy, molybdenum and a molybdenum-basedalloy.
 12. The method of claim 1 wherein said substrate is selected fromsilicon, aluminum oxide, enamel, mullite, a glass, fused silica, asilica-based refractory and a ceramic.